Manufacture of electric filaments.



UNITED STATES PATENT OFFICE.

CARL AUEB VON WELSBAGH, OF VIENNA, AUSTRIA-HUNGARY, ASSIGNOB, TO WELS-BACH LIGHT COMPANY, OF GLOUCESTER CITY, NEW JERSEY, A CORPORATIQN-QF 4 7NEW JERSEY.

MANUFACTURE OF ELECTRIC FILAMENTS.

'No Drawing;

To all whom it may concern:

Be it known that I, Dr. CARL AUER VON WELSBACH, a subject of the Emperorof Austria-Hungary, residing at Vienna, Austria-Hungary, have inventedor discovered a certain new and useful Improvement in the Manufacture ofElectric Filaments, of which the following is a specification.

My invention relates to the production of a dense, coherent metallicfilament for i11- candescent electric lamps, consisting of metallicparticles fritted together, and which incandesces at a temperature abovethat at which platinum volatilizes.

It had been known that osmium possessed several of the rerequisites forthis purpose but owing to its utter lack of ductility it has heretoforebeen impossible to. form it into incandescent filaments. It isexceedingly brittle, and therefore its-particles cannot be depended uponfor mutual adhesion (as can the particles of other metals; latinum, forinstance,) to permit of the forming of a wire by ordinary processes.Moreover, while it has been recognized that osmium is a good conductorof electricity, yet it was not known that it was non-volatile in wacuoor certain protective gases-at temperatures far above the temperaturesat which platinum volatilize's.

I have discovered that, at very high temperatures, in an atmosphere ofcertain protective gases, or in 'vacuo, it is possible to obtain acommercial osmium filament composed of the metal in a partially fused orcinder-like condition and wherein the particles are in' intimate contactsufiicient to obtain perfect electric conductivity and the requisiteflexibility and elasticity for the uses intended, while at the same timethe filament 'resists liquefaction even at such high temperatures. Thismaintaining of its solid form, when the heating is efi'ected in thepresence of certain gases or in a vacuum such as that of the ordinaryelectric lamp, and the refusal to liquefy or volatilize, continue up totemperatures much higher than that at which the volatilizationof-platinum pccurs; a fact which is utilized as one of the bases of thepresent invention.

To fiflly understand my-invention, it must be remembered that the metalosmium (among those of its group of highly infu- Specification ofLetters'Patent.

sible metals) is peculiar in that it oxidizes with great readiness, whenin the presence of free oxygen.

According to my present method, I employ an inner carrier or fillet uponwhich osmium 1s deposited, after which I remove V the inner carrier orfillet by the heat of an electric current, in the presence of suitablegases, and cause the particles of osmium to Patented Nov. 22, 1910.Application filed August 9, 1898. Serial No. 688,202. a

and capable of withstanding shocks and jars to which it is subjectedwhen in use. The crosssection of the filament is also dependent uponother conditions present, such as its length and the purity of theosmium employed.

I will now describe a method which may be followed in making filamentsof the kind to which this invention relates, although it will beunderstood that'I do not restrict myself to the precise steps ormaterials, inasmuch as equivalents for both can be readily substitutedby those acquainted with this art.

I first procure an organic thread or threads (I prefer vegetablethreads) of fine fibers, which should notbe too strongly twistedtogether, inasmuch as the pores or interstices should be as open aspossible for the reception of the coating or impregnating mass.

I make a mixture'of any of the sulfids of osmium (which although more orless insoluble in water can be suspended therein in an exceedingly finestate of subdivision) with a sinall quantity of suitable bindingmaterial, such as sugar. The whole is brought to a cream-likeconsistency by the addition of a suitable "quantity ofwater.

The ingredients are thoroughly incorporated so that the osmium sulfidmay be umformly distributed throughout the mass. I then immerse thethread or threads or coat them with this composition until they arethorpossibility of thorough impregnation) twov or more thereof can be toadvantage twisted,

woven or interlaced together so as to form a com osite thread or fabricwhich shall be of su cient cross section to result in a fila- 'ment ofthe required dimensions.

This

weaving, lacing or twisting should occur after the threads have beenimpregnated orcoated with the composition, and to render the thread orthreads more uniform they may be drawn while moist, through a dieorsubjected to the action of a suitable mold,

to give a uniform cross section and consequently a uniform resistancethroughout. After being sufiiciently impregnated or coated and shaped asdesired, the threads.

are dried, and are then subjected to dry distillation The threads thusprepared are thereafter placed in an .electric circuit and heated to apoint at which the carbon is eliminated and the reduction of the osmiumAzompound occurs. To assist in such reduction and preserve the metallicosmium, use is made of a suitable reducing atmos here, as for instancethe gases from a ashed back Bunsen burner, which contain hydrogen,carbon-dioxid, carbon monoxid, hydrocarbons and water vapor. Thefunction of the water vapor is to remove the carbon by oxidation andto'form with it an inert gas. After the removal of the carbon I thencarry the heat to a point at or beyond that at which platinumvolatilizes to complete the cementation or cohesion of the particles ofmetallic osmium.

Having completed the foregoing treatment, it will be found that themetallic osmium has assumed a thread-like form and is coherentthroughout and of su-ificient flexibility and elasticity to adapt it foruse as an incandescent electric filament. The fi1aments thus producedare readily distinguishable in that they are devoid of carbon,-have thenecessary flexibility and resiliency or elasticity, and depend uponmetallic osmium not only for their conductivity, but for theincandescence which is produced at a tem perzture at which platinumwould be volatilize I have mentioned sulfid of osmium as one of thecompounds which I can employ, but

I wish it to be understood that substitutions can be made therefor ofany suitable com pounds of this metal, as, for instance, the tetroxideor the metal itself in afinely divided condition, can be used.

Now while I have set forth one method and certain materials which can beemployed, I wish it to be understoodthat I do not limit myself to thatprecise method or to the materials specified, as my invention includesthe use of both ruthenium and rhodium in the place of osmium, and

permeated or coated thereby; When i osmium tetroxid.

methods which are substantially the equivalent of that herein set forth.

"While ruthenium and rhodium can be substituted for osmium, and. treatedin the same manner for the production of an incandescent filament, yetsuch filaments are by no A means as effective as those of osmium,.sinceboth ruthenium and rhodium although melting at temperatures higher thanplatinum melt at tem eratures much below that of osmium. All oys ofosmium, ruthenium, and rhodium may also be used. The efliciency of thefilament however, depends upon its withstanding extremely hightemperatures and temperatures above that at which plat inum volatilizes.v

To the composition. to be used, may be addedcertain of the refractoryrare earths, such as 'thoria, zirconia, and the ytterite earths. If, atthe termination of the treatment of the filament in the reducingatmosphere, it is found that it is not of uniform resistance throughoutits entire length, the requisite equal conductibility may be obtained bysurrounding it again with an atmosphere of the same reducing gases andvapor, and again highly heating the filament by he electric currents andfrom time to time introducing small quantities of volatile osmiumcompounds, as for instance, The filaments are now ready for mounting inthe ordinary incandescent bulbs which should be thoroughly exhausted orfilled with inert gases when ready for use.

In the course of my experiments, I have devised other methods for themanufacture of my osmium filament which are set forth in an applicationfor Letters Patent filed herewith, Serial No. 688,201, and whereinI havemade claim s ecifically to my within described, dense, co erent, compactosmium filament which incandesces at a temperature at which platinumwould volatilize.

What I claimherein is: 1. The herein described method of manufacturingincandescent electric filaments, consisting in "associat' organic threadwith osmium; then, sub ecting the thread to dry distillation; and then,by the action of the electric current, in a suitable atmosphereeliminating the carbon and uniting the metallic particles into acoherent filament of metallic osmium; substantially as set forth.

2. The herein described method of manufacturing incandescent electricfilaments, consisting in associating organic thread with'osmiumchemically combined with another substance to form a reducible conipound and thereafter subjecting the same to dry distillation; then, bythe action-of the electric current in a suitable atmosphere eliminatingthe carbon and reducing the said compound to the metallic state; andthen,

the thread to dry distillation; and thenv placing the same in a suitableatmosphere wherein, by the action of the electric current the carbon iseliminated, whereby the metallic particles of osmium are united into acoherent filament of metallic osmium, substantially as set forth.

4. The herein described method of manufacturing a metallic electricfilament, consisting in associating organic thread with metal having ahigher point of fusion than that of platlnum, and, subjecting the sameto dry distillation, and placing the same in a suitable atmospherewherein the carbon is eliminated, and by the action of the electriccurrent at a temperature at which platinum would volatilize, causing themetallic particles to unite'into a dense, compact, coherent'filamentsuitable for electric'incandescence; substantially as set forth. I

5. A dense, coherent metallic filament for incandescent electric lamps,consisting of metallic particles fritted together and which incandescesat a temperature above that at which platinum volatilizes; substantiallyas set forth.

Signed this 27th day of July 1898.

CARL AUER VON l/VELSBAOH. Witnesses:

LUDWIG HAITINGE, ADOLF GALLIA.

